UKIP deputy leader Paul Nuttall has ruled himself out of the race to replace Nigel Farage as party leader.
Mr Nuttall, who was viewed as one of the favourites to succeed Mr Farage, said he had achieved his objective of getting the UK out of the EU.
The North West England MEP also said he would resign as deputy leader at the party's next national conference.
He would keep his European Parliament seat to "hold the government's feet to the fire" during Brexit talks, he said.
The UKIP leadership contest was triggered last week when Nigel Farage announced he was standing down.
'Head held high'
He said his "political ambition has been achieved" in the wake of the EU exit vote, and he wanted his "life back".
Mr Nuttall had been backed by Neil Hamilton, UKIP group leader in the Welsh Assembly, as being "streets ahead" of anyone else in the contest.
Speaking at the party's North West conference in Liverpool, Mr Nuttall said: "I have been at the forefront of the campaign to leave the European Union for a decade now, and I believe I can step aside with my objective achieved and my head held high."
He added: "I will however remain leader of the UKIP delegation of MEPs in the European Parliament so that I can continue to hold the government's feet to the fire during the Brexit negotiations."
Mr Nuttall, who has also served as UKIP's chairman, was elected to the European Parliament in 2009.